This invention relates to handling and processing systems for mixed mail and related articles, and more particularly to a singulation mechanism for use in such systems which facilitate the handling of articles having significant variation in size, thickness and weight.
Mixed mail received at a post office or other location must be sorted and/or otherwise processed so as to be directable to a desired location. To accomplish this function, random items of incoming mail are typically stacked, either manually or otherwise, for feeding to a first mechanism which singulates the mail so that only a single piece of such mail, which is properly oriented and spaced, is passed on to the sorting or other processing mechanism of a mail handling system.
While many mechanisms currently on the market do an adequate job of singulating certain types of mail, increasing demands are being placed on such systems, both as to the ranges in size, thickness and weight of the mail pieces to be handled and as to the speed at which such systems are to operate, while still maintaining high controllability on the outputted mail pieces, a low jam rate, low damage rate and substantial elimination of doubles passing into the sorting mechanism. For example, a specification for mail pieces to be handled in such a high performance system might include pieces ranging in thickness from 0.007xe2x80x3 to 1.25xe2x80x3, pieces ranging in weight from 0.03 oz to 6.0 lbs., and pieces ranging in size from 3.5xe2x80x3xc3x975.0xe2x80x3 or 4.0xe2x80x3xc3x974.0xe2x80x3 to 15xe2x80x3xc3x9715xe2x80x3. These variations in thickness, weight and size must be handled without sacrificing throughput, which may be up to approximately 14,500 mail pieces per hour, although this maximum rate may vary somewhat with the size of the pieces being processed, and preferably with an ability to control this rate. A system capable of reliably achieving this level of performance without jams and other problems does not currently exist. Further, while the requirements discussed above are particularly applicable to mail handling systems, they can also arise in handling systems for packages and/or other generally flat articles.
In accordance with the above, this invention provides a singulation mechanism for use in a handling system for mail or other substantially flat articles. Mail/articles are fed, for example by a suitable feed mechanism, from a stack to a singulation head, the first piece of mail/article being preferably pressed from the stack against the head. In the broader sense and in accordance with a first aspect of the inventions, the singulation head includes a drive mechanism which initially moves a piece of mail or other article pressed thereagainst with high acceleration, interrupts the drive to the piece mail/article for a brief instant, and then moves the piece of mail/article again at high acceleration, a take-away mechanism removing mail/articles exiting the head. At least one position detector may be provided for articles moved by the head, drive interrupt and restart at the head being in response to a selected position detection by such detector. The drive mechanism may include a plurality of drive components, including at least a first rear component and a second forward component, the first component being initially energized to move the article, then de-energized to interrupt drive and the second component then being energized to move the article again. The drive mechanism may include a drive belt moving at a selected rate across the head, and the first and second components may be components selectively applying vacuum pressure through an adjacent portion of the belt. Where a doubled piece of mail may be hung up between the singulation head and the take-away mechanism, a detector may be provided which detects the presence of a piece of mail in between the head and take-away mechanism, and a control may be provided which is operative in response to an output from the detector, after detection that a piece of mail being singulated has reached a predetermined position in the take-away mechanism, for energizing the second component to move the doubled piece to the take-away mechanism.
More specifically, the singulation head to which a stack of mail/articles is fed may include a belt having a predetermined pattern of openings formed therein, which belt is driven across the head at a selected rate, and first and second vacuum chambers positioned behind the belt so as to apply vacuum therethrough when energized, the first vacuum chamber V1 trailing the second vacuum chamber V2, the belt therefore passing over V1 before V2. An article fed to the head is pressed against a surface of the belt opposite that passing over V1 and V2. A first detector is provided for detecting when an article being singulated by the head reaches a selected first point near a leading edge of the head. A take-away mechanism is provided for articles exiting the head and a second detector is provided for detecting the articles reaching a selected second point of the take-away mechanism. Controls are also provided for selectively energizing V1, for de-energizing V1 and energizing V2 in response to an output from the first detector and for de-energizing V2 in response to an output from the second detector.
The vacuum chambers when energized are preferably at a vacuum pressure of approximately 10 Hg to 25 Hg. For applications such as mail handling, the vacuum pressure depends at least in part on the selected weight range for the articles. Where the articles have a maximum weight of approximately 6 lbs., the vacuum pressure range is approximately 15 Hg to 24 Hg. The vacuum flow for the vacuum chamber is preferably in a range of approximately 14 cfm to 17 cfm. For an alternative embodiment, the controls also momentarily stop and restart the belt in response to an output from the first detector. The surface of the belt against which articles are pressed preferably has a low coefficient of friction, being substantially friction free, whereby, absent vacuum applied through the belt from a vacuum chamber, the belt does not impart substantial movement to an article pressed against it. The head preferably has at least one pressure sensor to detect the pressure at which articles are pressed against the surface of the belt, there preferably being a pressure sensor below the belt and at least one pressure sensor above the belt. There is also preferably at least one low pressure vacuum chamber trailing the belt to apply drag force to doubles and at least one low pressure vacuum chamber above and below the belt to stabilize articles and to further apply drag forces to doubles. A doubles resolver head may also be provided between the singulation head and the take-away mechanism to further assure against doubles reaching the take-away mechanism. For singulation of mail, the belt for the singulation head preferably operates at 78 to 85 in/sec and the take-away mechanism preferably operates at approximately 100 to 102 in/sec.
In accordance with a second aspect of the invention, the singulation head includes a drive mechanism which, when energized, moves a first article in a stack to be singulated at high acceleration and, when not energized, imparts substantially no movement to the article and a control for energizing the mechanism only when the first article is to be moved. For a preferred embodiment, the head includes a belt having a predetermined pattern of openings formed therein, which belt is driven across the head at a selected rate. The belt has a first side with a substantially friction-free surface against which the articles are pressed and a second side which is opposite the first side. A source selectively applies low pressure to the second side of the belt when an article is to be moved by the belt, the belt being substantially ineffective to move an article pressed against the friction-free surface thereof when low pressure is not applied to the belt. For preferred embodiments, the low pressure is a vacuum pressure and at least the friction-free surface of the belt is of a substantially friction-free material. Where the head is being used to singulate mixed mail, the belt is preferable approximately 3xe2x80x3 wide and continuously perforated.
The invention also includes a belt for use in a singulation head of a substantially flat article handling system, which belt includes a first side having a substantially friction-free surface against which the article is pressed and a second side opposite the first side to which the head selectively applies at least substantial vacuum pressure. A pattern of openings is formed in the belt between its first and second sides. Where the belt is being used for the singulation of mixed mail, the belt may for example be approximately 3xe2x80x3 wide and continuously perforated.
The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.